1. Field of the Invention
The present invention relates to a lens assembly for an image sensor, which is comprised of an aperture, a first lens, a second lens and a third lens, each lens of this assembly has an improved capability of restraining the power, so that the sensitivity of decentration and the aberration-correcting effect of the whole lens assembly in accordance with the present invention can be effectively improved.
2. Description of the Prior Arts
Image sensor has been widely used in different areas nowadays. For example, the mobile phone also has been equipped with such an image sensor comprised of a solid state imaging device and lens, such as Charge Coupled Device (CCD) sensor or Complementary Metal Oxide Semiconductor (CMOS) sensor. With the development of science and technology, the mobile phone is becoming more and more smaller, thereby, the lens in the mobile phone also needs to be miniaturized.
For example, JP Patent 2004-4566 discloses an image lens assembly consisted of three miniaturized lenses which are arranged sequentially from the object side: 1, an aperture; 2, a first biconvex lens having a positive refracting power; 3, a second lens having a negative refracting power whose concave surface is located on the object side; 4, a third meniscus lens whose convex surface faces the object side.
However, this lens assembly has some disadvantages. For example, the power of the first lens is excessively strong. Meanwhile, aberration-correction should be carried out in order to modify the power of the first lens, consequently, the power of the second lens also should be strong. However, if all the respective lenses are strong in power, the sensitivity of decentration of the whole image lens assembly will be excessively increased, so that the function and effect of the lens assembly is consequently affected in a detrimental way.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.